Using Gatsby Remark Images

To enable gatsby-remark-images, you first need to install the relevant
image plugins:

yarn add gatsby-plugin-sharp gatsby-remark-images

If you don't have gatsby-source-filesystem installed, also install that.

Then configure the plugins. gatsby-source-filesystem needs to be
pointed at wherever you have your images on disk,
gatsby-remark-images needs to be a sub-plugin of gatsby-mdx, and
gatsby-plugin-sharp can be included on it's own.